Double gas hydrate of isopropanol and methane

Abstract

Composition and structure of isopropanol and methane double hydrate synthesized from isopropanol solutions with concentrations from 6.2 to 17.9mass.% were studied by means of thermovolumetric and X-ray powder diffraction methods. It was found that the double hydrate has a cubic structure II within the whole concentration range. Composition of the double hydrate with the maximal methane content corresponds to 4.5C3H7OH·17.0CH4·136H2O (274.2K and 5.2MPa). We studied the decomposition curve of this hydrate in the temperature range from 253K to 280K. At temperatures above 273.2K, double hydrate decomposition temperatures are only 1–2K higher than that of pure methane hydrate. However, at temperatures below 273.2K, double hydrate decomposition temperatures are significantly higher in comparison with methane hydrate. For example, at 1MPa, methane hydrate decomposes at 243K while double hydrate decomposes at 267.0K. Our findings show that isopropanol is a promising hydrate-forming component whose aqueous solutions may be advantageously used in separation processes using gas hydrate formation technology at temperatures below 273.2K and for gas storage in the form of double gas hydrate.